What is the principle behind the expansion and contraction of balloon in the bottle used for lung model

Question

The picture above describes inhalation and exhalation, the balloons present the lungs which deflate during exhalation when the elastic bottom(diaphragm) is release and vice versa for inhalation what is the principle behind the conservation of pressure in the balloons and in the bottle

Answer 1

1. Air (or any fluid) in equilibrium exerts an equal pressure in all directions.
2. Any difference in pressure between the gas jar and the balloons will cause the balloons to expand or contract.
3. As the balloon expands, the elastic force acts so as to return the balloon to its natural shape.
4. The pressure exerted by the gas is inversely proportional to the volume it occupies (bigger volume means fewer particles per unit volume, so less force on the container).

Using this, it is simple to understand how the model works. As the elastic membrane is pulled down, the volume of the chamber increases, thereby reducing the air pressure inside the chamber. Therefore, the force of the air in the balloons (atmospheric pressure) is greater than the pressure in the chamber, so the balloon expands.

As the balloon expands, the elastic force increases, eventually compensating for the difference in pressure between the atmosphere and the chamber.

When the membrane is released, the reverse happens. The volume of the chamber decreases, so the pressure in the chamber increases, which forces the balloons to contract.